In a mobile communication system, a macro base station is usually installed in an equipment room under a tower, or outdoors under a tower (with no equipment room). In this case, the macro base station under the tower and an antenna on the tower need to be connected through a long high-power radio-frequency (RF) cable (feeder). However, the loss rises with the increase of the length of a feeder, and is generally around 3 dB.
In order to reduce the feeder loss to the minimum, the base station tends to be moved onto the tower. An existing radio remote unit (RRU) and an integrated antenna (RRU+Antenna) to be proposed are such products. More advanced products include an active antenna and an intelligent antenna.
As shown in FIG. 1, the RRU is located at a link between a passive antenna and an indoor baseband unit (BBU). Interface signals between the RRU and the passive antenna are RF signals, and the RRU is connected to the passive antenna through a feeder. Interface signals between the RRU and the BBU are common public radio interfaces (CPRIs) or other digital signals, and the RRU is connected to the BBU through an optical fiber (definitely, the RRU and the BBU may also communicate through an electrical interface or other digital signals). As shown in FIG. 2, external interfaces of the integrated antenna, the active antenna, or the intelligent antenna are CPRIs or other digital signals, and can be connected to the BBU through optical fibers.
Macro base stations invested and constructed by operators in the early stage and the currently popular RRU products may not be abandoned due to the emergence of the integrated antenna (or the active antenna), as the early investment of the operators is huge, and the maximization of investment returns has to be considered. Because the macro base stations and RRU products are still used in the network, the commercialization of the integrated antenna, or the active antenna and intelligent antenna having more powerful functions is affected.
The functions of the macro base station and RRU are integrated in the integrated antenna, active antenna, or intelligent antenna, so that the functions of these antennas are more powerful. In the process of newly establishing a communication network, if the integrated antenna, active antenna, or intelligent antenna is configured to replace the passive antenna connected to the macro base station or RRU in the existing network, because the interface signals of the communication between the macro base station or RRU and the passive antenna are RF signals, after the replacement, the integrated antenna, active antenna, or intelligent antenna is not compatible with the existing macro base station or RRU. As a result, the macro base station or RRU becomes unnecessary, which causes waste of resources.